Automatic transmission



ci. 26,' 1%43. NUTT ET AL AUTOMATIC TRANSMISSION Filed Jan. 4, 1941 5Sheets-Sheet l ct, 26, 1943.. H. NUTT ET AL 2,332,593

AUTOMATIC TRANSMISSION Filed Jan. 4, 1941 5 Sheets-Sheet 2 Ust. 26,1943., H. NUTT ET AL AUTOMATIC TRANSMISSION 5 Sheets-Sheet 3 Filed Jan.4, 1941 Ct 25, w43 H. Nuur'r ET AL AUTOMATIC TRANSMISSION Y 5Sheets-Sheet 4 Filed Jam/1, 1941 fic/afd A. A35" ct., 26, 1943. H, NUTTET AL 2,332,593

AUTOMATIC TRANSMISS ION Filed Jan. 4, 1941 5 Shees-Sheet 5 WM @WPatented Oct. 26, 1943 AUTGMATIC TRANSMISSION Harold. Nutt, Chicago, andRichard L. Smirl,

Bellwood, Ill., assignors to Borg-Warner Corporation, Chicago, Ill., acorporation of Illinois REISSU-ED Application January d, 1941, SerialNo. 373,201 2 7 ma l2 Claims. (Cl. 74-189.5)

fluid. The problems attendant upon the use of a hydrodynamic device inan automatic transmission include among others that of gettingsufficient torque multiplication to satisfy the requirements for anautomobile and to do this at satisfactory emciencies. This has led tothe use of gearing in addition to the torque converter and to variousclutching arrangements for substituting another drive for the torqueconverter at the speeds at which the torque converter is inemcient. Withthe addition of these devices the transmission becomes more complex andexpensive.

Another problem encountered in the hydrodynamic type of transmission isthat of operating an associated positive control element to eect a shiftas, for example, from neutral to reverse. At idling speeds of the engineenough toroue is transmitted through the hydrodynamic device to renderthe engagement of a positive toothed control device dimcult, if notimpossible.

'I'he principal object of this invention is to provide an automatictransmission which utilizes the advantages of a hydraulic torqueconverter and makes full provision for its several shortccmings with aminimum complexity of controls.

Another object of this invention is to provide torque converter type inwhich a satisfactory reversing mechanism is employed.

Another object of this invention is to provide a simplified hydraulicsystem for operating an automatic transmission, the system including aclutch which utilizes the pressure within the torque converter to changeits condition.

Yet another object of this invention is the provision of improved meansfor starting an enlan automatic vtransmission of the hydraulic y ginethrough the transmission by pushing the car when taken together with theaccompanying drawings in which:

Fig. 1 is a plan view in section of the transmission.

Fig. 1a is a fragmentary section taken along line Ia-Ia of Fig. 1.

Fig. 2 is a schematic layout of thehydraulic system;

Fig. 3 is a vertical section through the valve block taken along line3--3 of Fig. 4.

Fig. 4. is a side view of the rea'. portion of the transmission showingthe valves and a portion of the controls therefor taken along line ,llofFig. 3;

Figs. 5 and 6 show the linkage for operating one of the valves in thetransmission; and

Figs. '7, 8 and 9 are schematic diagrams showing the operation of themanual over-control for one of the clutches.

Referring now tothe drawings for a detailed description of the'invention and particularly to Fig. 1, the transmission in its preferredform is comprised in general of a drive shaft I0, a driven shaft I I, ahydrodynamic torque converter I2 located within bell housing I3, a valveblock I4 secured to bell housing I3, a planetary change speed gearingI5, and a planetary reverse gear I6. Various clutches and controls areincluded for operating and controlling the torque converter andplanetary gear set including a positive clutch Il for locking up thetorque converter, a hill brake I8 to be used in conjunction with torqueconverterA I2, a, brake I9 for conditioning planetary gear set I5 foroverdrive operation, a roller and cam type automatic clutch 20 forconditioningplanetary gear set I5 for direct drive, a releasable clutch2l which may be released to disconnect'the driven shaft II fromplanetary gear set I5 to provide a neutral, and a positive brake 22 ofthe toothed type for arresting one of the elements of the planetary gearset I6 to provide a reverse drive.

The power is transmitted from drive shaft I0 to a forging 23 bolted to aflange on drive shaft I0, said forging 23 supporting in turn a flywheel2l-and a varied pump member 25 bolted to fly.- wheel 24. These lastthree elements form a chamber which is normally filled with iluid underpressure. Opposite varied pump member 25 is a vaned turbine member 26which comprises the driven element of the hydraulic torque converter I2.Torque conversion or multiplication issecured by means of avaned stator21 interposed between the exit of the turbine vanes and the entrance tothe pump vanes. Turbine member 28 is riveted to a carrier 28 which issplined to 'an intermediate shaft 28. Stator 21 is splined to I by meansof a roller-and-cam type one way brake 3| reacting against a plate 32non-rotatably mounted in bell housing I3. l

Carrier 28 is formed with radial bores 33 in which are mounted pistons34 having at the outer extremities thereof chamfered teeth 35 (Fig. 1a)which are adapted to engage slots 33 in forging 23. Said pistons 34 arebiased to a retracted position in carrier 28 by a spring 31 passingthrough a suitable opening 38 in the carrier and intermediate shaft 29.The chamfer on teeth 35 is in such a direction that when drive shaft I9is rotating faster than intermediate shaft 28, teeth 35 will not engagewith s1ot'36 to form a clutching connection between drive shaft l0 andintermediate shaft 29, but will permitv such clutching connection whenthe speed of drive shaft I0 drops down to the speed of intermediateshaft 29.

Intermediate shaft 29 extends rearwardly to planetary gear set I anddrives the carrier 39 of this gear set. Upon carrier 39 are mountedplanet gears 40 which mesh with a ring gear 4I and with a sun gear 42.Saidigun gear 42 is formed from a sleeve 43 which is flanged and rivetedt the rotatable element 44 of brake I9. Ring gear 4| is splined to adrum 45 which constitutes the driving element of disc clutch 2|, thedriven element 46 being splined to driven shaft Also splined to drum 45is a connecting casting 41 which transfers the drive from drum 45 to thesun gear 48 of planetary gear set I5. Said sun gear 48 meshes withplanet gears 48 mounted on a carrier 50 which is free to rotate aboutdriven shaft I I. Planet gears 49 in turn mesh with a ring gear 5I whichis splined to a flange 52 rotatable with driven shaft |I.

The rotatable element of reverse brake 22 is comprised of a toothedmember 53 which may be in the form of an ordinary spur gear, mounted torotate with carrier 50. Beside driven shaft and aligned with toothedmember 53 is a sprag 54 slidably mounted in gear housing 55 and fixedagainst rotation. When sprag 54 is moved toward toothed member 53 so asto engage the teeth thereof, carrier` 50 is held against rotation anddriven shaft |I will be driven in a reverse direction with respect todrive shaft I0 when the drive of shaft I0 is impressed on sun gear 48.

The various conditions of operation of the transmission are as follows:

For neutral and all forward speeds, sprag 54 ls Withdrawn from toothedmember 53. With sprag 54 withdrawn, neutral is obtained by releasingclutch 2| which breaks completely the connection between the drive anddriven shafts.

For forward speed in the lowest ratio, torque concerter lockout clutchI1 is released, brakes I8 and I9 are released and clutch 2| is engaged.The drive is then transmitted from drive shaft I0 through the torqueconverter to intermediate shaft 29, and thence to planet gears 4D ofplanetary gear set I5. At this point the load of the driven shaft istransmitted through clutch 2| to ring gear 4| and accordingly sun gear42 will tend to rotate ahead of carrier 39. This, however, is preventedby roller-and-cam clutch 29 which locks the carrier to the sun gear,thereby effecting direct drive through planetary gear set I5. In thelowest ratio possible, therefore, the drive between drive shaft I0 anddriven shaft II is effected through, and the torque is multiplied by,torque converter I2. It will benoted that stator 21 is held againstrotation by one way brake 3| as long as torque conversion takes place inthe converter andthat thereafter itis free to rotate with the -impeller25 of the converter.

For the next ratio, clutch I1 is engaged to couple drive shaft I0directly with intermediate shaft 29 and thereby lock up torqueconverter,|2.

The clutch is centrifugally conditioned for-engagement considerablybelow the end point of the torque conversion speed of the converter, butit can be engaged at the will of the driverl at any speed above thisconditioned speed by momentarily releasing the throttle, therebypermitting synchronization to occur. 'Ihe clutch will remain engaged atall speeds abovethe centrifugally conditioned speed unless forced backby the means and under the conditions to be hereinafter described. Thepawls will remain engaged below the conditioned speed so long ascontinuous torque is being transmitted. When the vehicle is stopped, thetorque between members 34 and 38 will reverse at some point before thevehicle comes to rest, thus enabling the clutch to releaseautomatically.

The next and highest ratio is obtained by en- A gaging brake I9 to holdsun gear 42, thereby conditioning planetary gear set l5 for overdrive aswill be described in detail later.

Reverse is obtained by releasing clutches I1 and 2| (the formerreleasing automatically when the car is at rest) and releasing alsobrake I9. Sprag 54 is engaged with toothed member 53 to hold car-y rier59 and the drive is therefore reversed through planetary gear set I6,the drive being through connecting casting 41 to sun gear 48.

The description thus far has been concerned merely with the mechanismfor transmitting the torque from drive shaft l0 to driven shaft I I. Thecontrols for effecting the various shifts described above and others tobe described hereinafter will now be detailed.

With the exception of the spragvand the roller and cam devices thevarious clutches and brakes are controlled, or operated and controlled,by hydraulic pressure. The controls therefor comprise in the main,pumps, valves, and passages so interconnected with the various clutchesand brakes as to supply operating pressure to the proper device at thetime desired and also to remove operating pressure from certain devicesin an emergency and under the control of the operator to eifect adown-shift. For example, means are provided for releasing brakev I9 toreduce the drive from over-y drive to direct drive, and additional meansare provided to release clutch I1 to restore the drive through thetorque converter, both of these down shifts being under the controlofthe operator.

Referring now to Fig. 2, the various clutches and brakes are shownschematically, together with the hydraulic circuits to and from theseelements and their respective control valves. Dual hydraulic systems areprovided, fluid pressure for the first system being derived from a pump55 which is driven by means of gears 51 which in turn are driven from asleeve 58 drivingly connected to impeller member 25 of hydraulic torqueconverter I2. Pump 55 therefore is operated whenever drive shaft I0 isturning. The oil from pump 59 is maintained at a pressure ofapproximately 60 pounds per sq. inch by means of a relief valve 59( Apressure line 50 conducts the oil from pump 56 to a branch 5| which isdivided side outlet 65 to approximately 30 pounds per sq. inch. Oil atthis pressure is then conducted through conduit 66 to a chamber 61surrounding pump gear 51 and communicating through a passageway 68 withthe interior of the hydraulic torque converter I2. It will be noted thatthe entire chamber formed by flywheel 24 and lmpeller 25 is filled withfluid at 30 pounds per sq. inch pressure, which means that the outersurfaces of the pistons forming clutch I1 are acted upon by thispressure whenever pump 56 is in operation. As will `be described ingreater detail later, this pressure tends to assist springs 31 toretract the pistons to release the clutch I1 and is' utilized to effecta down-shift of this clutch under certain circumstances.

A second branch `|59 in pressure line 60 conducts fluid at 60 pounds persq. inch pressure to valve chamber in which is located the control valve1I for main clutch 2|. Said valve 1| has la central portion 12 ofreduced cross section to permit the uid to pass therearound into conduit13 which communicates with a central bore 14 locatedin shaft 29. Drivenshaft II contains a similar bore 15 in communication with bore 14 andconducts the fluid to an annular chamber 16 which is mounted forrotation with drum 45- of clutch 2|. Within annular chamber 161s anannular piston 11 which is slidable axially to compress the driving` anddriven members of clutch 2| together and thereby couple driven shaft IIwith drum 45 and its associated ring gear 4I (see Fig. 1).

Valve 1I is shown in the position it assumes when the transmission isconditioned for forward drive by the operator. The valve is slidable tothe right to close off branch 69 and simultaneously to permit the fluidbehind piston 11 to escape beyond the right hand edge (Fig. 2) of valveblock I4. This releasing action is augmented by a retractor spring 18(Fig. l) which is fixed at one end 19 relative to chamber 16 and theother end of which bears against piston 11.

Thus when the main clutch control valve 1I is positioned as shown inFig. 2v and pump 56 is operated, fluid under pressure is conductedsimultaneously to the hydraulic torque converter I2, to the outersurfacesof clutch pistons 34 of clutch I 1, and to chamber 16 of clutch2| to operate the latter clutch.

Under normal conditions fluid under 30 pounds per sq. inch pressure willbe conducted through a branch 80 to a second Valve chamber 8| in whichis located a valve 82 for controlling the positive clutch I1. Said valve82 is normally located to the right (shown in dotted lines) of theposition shown in Fig. 2 so that the portion 83 of reduced cross sectionis in alignment with branch 80 and also with a side outlet 84 whichcommunicates with a central bore 85 in the forward end ofintermediate'shaft 29. This bore is in communication with opening 38 andconducts the fluid under 30 pounds per sq. inch pressure to the underside of pistons 34 of the torque converter lock up clutch I1. Pistons 34are thereforebalanced insofar as the pressure within the converterchamber is concerned and are subject only to the action of centrifugalforce on the one hand and the retracting action of spring 31 on theother hand. Said spring 31 is of such strength as to maintain pistons 34in retracted position until the vehicle is moving at a speed ofapproximately 18 miles per hour, at which speed centrifugal forceovercomes the retractive effort of spring 81 and moves the pistonsradially outwardly to engage teeth 35 with slots 36.

Thus when valve 1| is positioned as shown and valve 82 is in the dottedposition, pump 56 being in operation, main clutch 2| Will be operatedand the hydraulic torque converter I2 will likewise be operated totransmit the drive at what corresponds to low speed from drive shaft I0to 'driven shaft II. Simultaneously, pistons 34 of clutch I1 will bebalanced hydraulically but 4will be subject to centrifugal force, andwhen the speed of the vehicle becomes sufficiently great, clutch I1 willbecome operative to lock up the hydraulic torque converter .and transmitthe drive of drive shaft I ll directly to intermediate shaft 29 insteadof through the intermediary of the torque converter.

To .obtain the next and highest speed ratio through the transmission,clutch I9 is operated to arrest the rotation of sun gear 42. 'I'his isaccomplished, hydraulically by the second hydraulic system previouslyreferred to, which is controlled by a piston type valve in the firsthydraulic system.

The second hydraulic system is comprised of a pump 86 which is driven bygears 86' (Fig. 1) drivingly connected to driven shaft II so as to makepump 86 responsive to vehicle speed. The pressure of the fluid suppliedby pump 8B is maintained at approximately 50 pounds per sq. inch by arelief valve 81. It will be noted that this pressure is ten pounds lessthan that in the first system. A pressure line 88 conducts the fluidunder pressure to a conduit 89 in valve block I4. Said conduit 89 is incommunication at one end with branch 63 of the first hydraulic system, avalve 90 being interposed between the two systems. Said valve 90 is freeto move to the left a distance sufficient to uncover a side outlet 9|communicating with branch 62 in the first hydraulic system, and by thismeans, fluid pressure may be supplied from the second sys-,- tem to thefirst whenever the engine is not in` operation and it is desired toeffect normal operation of the transmission. Thus when it is desired tostart the engine by pushing the car, driven shaft will be rotated andwill cause pump 86 to operate, which in turn will supply fluid underpressure to conduit 89 and will move valve 9 0 to the left (Fig. 2,) touncover outlet 9| and permit the fluid under pressure to enter the firsthydraulic system. After the engine begins to operate and pump 56supplies fluid at 60 pounds per sq. inch pressure'to branch 63, the tenpound pressure differential will move valve 9| to the right until itstrikes abutment 92 in conduit 89. In this position outlet 9| is blockedand a bleed outlet 93 is uncovered by means of a section 94 of reduceddiameter in valve 98. A

bleed opening 95 connects conduit 89 with bleed outlet 93 to prevent arapid building up of pressure in the second hydraulic system after thecar begins to move. The purpose of the delay in establishing a 50 poundpressure in the second system is to prevent the operation of theoverdrive clutch I9 until a speed of approximately 18 miles per hour isreached. However, if pump 56. of the first hydraulic system is not inoperation, valve 90 will be in its right-hand position (Fig. 2) andbleed opening 93 will be covered so that there is no delay in buildingup the pressure in the first system under these circumstances and thetorque converter and main clutch are immediately effective to crank theeng ne.

The overdrive outlet of conduit 89 is controlled by overdrive lcutinvalve 96 which is biased by a spring 91 to closed position and under lowpressure conditions covers outlet conduit 98 and prevents uid fromentering therein. When a pressure of 50 pounds per sq. inch is reached,however, valve 96 is moved against the resistance of its biasing spring91 to uncover outlet 98 and permit iiuid under 50 pounds per sq. inchpressure to pass through this conduit to an annular chamber 99 in valveblock I4. In chamber 99 is an annular piston |00 which is movableaxially to compress the driving and driven members of brake I9 andthereby arrest the rotation of sun gear 42 to establish overdrivethrough the transmission. Engagement will be graduated by the rate ofdelivery of pump 86 and vent 95, While the delay valve 96 insures thatadequate pressure will be available for full engagement, therebypreventing long slip periods when the car is being driven at a speedwhich is approximately the same as the cut-in speed.

To recapitulate, the second hydraulic system is used primarily tooperate brake i9 to establish overdrive at a particular speed of thedriven shaft. It may also be used to supply oil under pressure to therst hydraulic system if for any reason pump 56 of the rst system is notin operation and it is desired to operate torque converter I2 and clutch2| as for example, to start the engine by pushing the car.

The stator brake I8 is likewise operated by fluid pressure and iscontrolled by valve in valve block I4. Said valve |0| is slidable in itsbore to a left hand position (shown dotted in Fig. 2) wherein itconnects a branch |02 of branch 69 to a conduit |03 by means of asection |04 of reduced cross section. When so moved, fluid underpressure is conducted to a chamber |05 of annular cross section in whichis disposed an annular piston |06 which is adapted to compress thedriving element |01 and reaction element of brake |8-and thereby arrestthe rotation of stator 21. It will be recalled that at speeds above 18miles per hour clutch 1 is operated to connect pump 25 and turbine 26together which relieves stator 21 of backward reactive force and saidstator 21 is then free by virtue of the one-way holding characteristicof brake 3|, t0 rotate in a forward direction under the influence of thefluid in the torque converter. This forward rotation may be arrested bybypassing one way brake 3| and holding sleeve 30 through its splinedconnection with driving element |01 of brake |6. When so held a powerfulbraking action is secured which assists in keeping down the speed of thevehicle.

Having described the hydraulic circuits from the pump to the variousclutches and brakes, the means for controlling the valves which in turncontrol the hydraulic circuits will now be detailed.

Referring particularly to Figs. 1, 2 and 4, the forward, neutral," andreverse control may comprise the usual lever (not shown) at the steeringwheel of the automobile which is connected by suitable linkage (notshown) to a rock shaft |09 disposed vertically of the transmission andimmediately below sprag 54. Said rock shaft |09 is provided with twoarms ||0 and the first-mentioned of which controls the main clutch valve1| and the second of which is mechanically connected through a roller||2 and slot ||3 to sprag 54. Shaft |09 may be rocked throughapproximately 120 from a neutral position wherein sprag 54 is completelywithdrawn from toothed member 53, through a forward position whereinsprag 54 is not yet in engagement with toothed member 53 but is nearlyin contact with said member, to a reverse position wherein sprag 54engages the teeth of member 53 to arrest the rotation of planet car-Vrier 50.

Arm ||0 is connected through a, link ||4 to a lever ||5 the opposite endof which is connected to main clutch valve 1I. Said lever ||5 is in thenature of a floating lever and is supported by a. plate I1 in which is aslot I I8 for restraining the lever against lateral movement withrespect to valve 1| and link II4. The fulcrum for lever ||5 is providedby a roller I9 mounted on plate |I1. The connection with valve 1|comprises a sleeve |20 which is slotted at I2| and |22 to receive theupper end of lever ||5. A slotted plate |23 engages a notch I|6 in lever||5 and is resiliently urged to the right (Fig. 1) bya spring |24contained in a recess in valve 1|. Because of the relative location ofnotch |I6 and slot I2| the spring pressure will tend to rotate oatinglever ||5 in a counterclockwise direction (Fig. 1) but since suchrotation will be restrained by link ||4 and arm ||0, the net result willbe to tend to return valve 1I to the position shown in Fig. 1, i. e., tobias valve 1| to the left.

It will be noted that because of the particular linkage employed it willbe necessary to pass through the forward position in order to conditionthe transmission for reverse This causes clutch 2| to be engagedmomentarily each time it is desired to advance sprag 54 into toothedmember 53. Since the car at such time is presumably standing still, thiswill have the effect of momentarily stopping toothed member 53, thuspreventing unpleasant tooth clash, and then releasing said tooth memberto permit the sprag to enter the teeth, if for any`reason the teeth havebecome butt-ended. This arrangement of links and valves and its resultupon the action of the toothed member with which reverse sprag 54 is toengage, constitutes one of the principalfeatures of this invention. Bythis means the creep, which is usually present in a torque converterdrive and which would normally render substantially impossible theinsertion of sprag 54 into toothed member 53, is eliminated just priorto the actuation of reverse sprag 54 and a smooth operation of thereverse shift is assured. It will also be observed that the operation ofclutch 2| to arrest the rotation of toothed member 53 is perfectlysynchronized with the movement of sprag 54.

After the transmission has been conditioned for forward drive the torqueconverter lock up clutch |1 is automatically operated and in due coursethe overdrive brake I9 is likewise operated automatically. Situationsarise, however, Where it is necessary to shift out of overdrive intodirect drive in order to secure the benefit of the greater torqueobtainable in this ratio. may be eiected by the following instrumen'-talities:

Referring particularly to Figs. 2, 3, 5 and 6, chamber 99 associatedwith overdrive brake I9 is provided with an outlet passage |25 whichcommunicates with a transverse bore |26 in valve block |4. In bore |26is located a valve |21 which is rotatable through an arc ofapproximately 45. In one extreme position of valve |21 conduit |25 isaligned with a slot |28 in the valve, which communicates with the hollowinterior |29 The down shift with a main vent |32 and also throughsseries of openings andan annular groove |3| in valve |21 with anauxiliary vent |32' leading -to the exterior of valve block I4. Thepurpose of auxiliary vent |32' is to prevent leakage past the valve andshaft |33. In the other extreme position of valve |21, slot |23 is notin alignment with passageway |23 and hence the pressure in chamber 33 isnot affected but is controlled solely by overdrive valve 85.

Valve |21 is provided'with a stem |33 to which is pinned an arm |34.Said arm is in turn connected through a grasshopper type spring |35 to asecond arm |36.rotatably mounted on stem |33 and connected at its freeextremity through a rod |31 and associated linkage (not shown) to theaccelerator pedal of the automobile. Suitable stops |38 and |39 areprovidedxon valve block |4 to limit the angular travel of 'arm |34. Itis undesirable generally to have the valve move with the acceleratorpedal and accordingly spring |35 serves to prevent rotation of the valveto a down shifting position until the accelerator reaches its wide openposition, whereupon an overcenter condition will exist as shown in Fig.6 and spring |35 will be snapped to the left to the dotted position. Thepoint at which this action takes place may be made apparent by the pro-30 ditions, therefore, shunt circuit |34 is broken by vision of a springstop |40 which interposes a slight resistance to the movement of arm |35to its overcenter position so that if the driver does not wish to downshift he `will not depress the accelerator beyond the point of increasedpressure. In a similarI max'ifer grasshopper spring |35 wil1`prevent areturn to overdrive until the operator substantially releases theaccelerator pedal, which he will do naturally after he has no furtherneed for increased acceleration.

Assuming that the vehicle is traveling at a speed at which clutch |1 isengaged but overdrive brake i9 is not yet engaged, and the operatorwishes to down shift to the torque converter, it willbe necessary toremove the iiuid pressure from behind pistons 34 in order to obtain asumcient differential pressure to withdraw the pistons. Since clutch |1is a positive clutch, however, a mere dilerential in pressure will notbe sufcient if an `appreciable amount of torque is being transmittedthrough the clutch at the time. It will be necessary, in addition, toremove the torque for an instant from teeth 35 to enable the pressuredierential to become effective. Accordingly the following mechanisms areemployed to edect this down shift.vr

Referring momentarily to Fig, 2 it will be observed that valve 82controls the pressure behind pistons 34. In order to remove thispressure, valve 82 must `be moved to the left to block the pressure side33' and to vent conduit 84. Normally, valve 82 is biased to the right bya spring |4I, the movement to the right being limited by an arm |42which moves with a rock shaft |43. As shown in Fig. 1, rock shaft |43 isprovided with an armv|44 which is connected by suitable linkage |45 tothe accelerator pedal or to some other manual control (not shown). Whenit is desired to down shaft into the torque converter, the control ismoved and this movement is transmitted through linkage |45, arm |44,rock shaft |43 and arm |42 to valve 82, thereby moving the valve to theleft against the action of spring |4| (Fig. 4). This removes pressurefrom behind pistons 34 and establishes the pressure dierential whichwill be utilized to release the clutch.

c asuntos r S oi' the valve. The hollow interior communicates IReferring toetheflchematic diagr l sown in niguna anse, une movement ofme control notpplymcvesvalv l2 to the lett (Fig. 7) but also cutcthcignitimmomentnily tcremove g the tdrquepn methy IS. The current for ltheignition circuit- |46 is derived from a battery |41, s or 'other sourceof electrical energy. and a coil |43', the circuitv through which isinterrupted periodically 'in timed relationy to the .movement` 1o o! thecrank shaft ci the engine through an interrupter |43; Connected in.shunt with the circuit through the interrupter |43 is a second circuit|84 which includes a switch |53 mounted Ion a pivoted bell crank til.The condition o! 15 the shunt circuit ani-kcontrol thereior duringnormal4 operation of. the automobile is shown in Fig. 9. It will beobserved lthair'switch |54 is normally closed and completes the circuitup to a dash pot |52. In said dash pot |52 are contacts so |53 and |54whichare mounted on springs extending lateraliy' inwardly from the sidesof the dash pot. Opposite contacts |53 and |54 are contacts |l and |53,respectively, connected together electrically by means of a springsupport |51. A pin |53 controlled by spring |55 and piston |54 normallybears against the support for contact |53 to make the circuit betweencontacts |53 and |55, and to break athe circuit hetween contacts |54 and|55. Under normal conthe separation of contacts |54, |55, and interrupter |49 controls the circuit.

In order to cut the ignition it is necessary to keep the'primary circuitshorted by completing mtime shunt circuit |54. This of course must bedone in timed relation to the operation of valve 82 which controlspositive clutch l1. 'For this reason, the mechanical movements of switch|55 are controlled from the same linkage |45 which o controls valve 82.

Assuming that the control for valve 42 has been operated to down shiftinto nthe torque converter, bell crank |5| is rotated clockwise to theposition shown in Fig. '1. It will be notedA that lower con- 45 tact |6|is mountedvon a spring which is Just suiciently long to catch a washer|53 mounted on the end of a rod |53, which in turn is connected topiston |60. The clockwise movement of bell crank |5| will. thereforeraise piston |44 dll and simultaneously break the circuit through switch|54 and through contacts |53 and |55, thelatter by reason of the raisingof contact '|53 from contact |55, At the same time the circuit will belmade through contacts |54 and 55 |56. Upon continued rotation of bellcrank |5| in a clockwise direction, washer |62 will be freed and pistonwill descend toward contacts |53 and |54. The freeing of washer |42 willalso cause the circuit to be completed through switch 60 |50. Downwardmovement of lthe piston will be retarded due to the dash 'pot action,and a predetermined time interval will elapse between a release ofwasher |32 and the reengagement of pin |58 with contact |53. As piston|54 descends o5 beyond thisy point, it will rst complete the circuitbetween contacts |53 and |55, which thereby shunts the ignition circuitas shown in Fig. 8, the other pairs of contacts having been previ' ouslymade, and then upon iinal downward movement will break the circuitthrough contacts |54 and |56. During the interval in'which the shuntcircuit is in the condition shown in Fig. 8, torque will be removed-fromteeth 35 and, the pressure having been'previously removed from behindthe pistons, said pistons will `be retracted under the combinedinfluence of the pressure. within the torque converter and theretractive effort of springs 31. The duration of the shorting of thecircuit is only a matter of a few'explosions of the engine so that therunning of the engine is not seriously affected.

It will be noted that shunt circuit |64 is established in dash pot |52on the upward movement of piston |60 as well as on its downward movementand hence. were it not for switch |50, the ignition circuit would beshunted and the torque removed from pistons 34 before the fluid had anopportunity to escape from behind the pistons. Switch |50 is soconstructed, however, that it will be opened before piston |60 begins tomove and will remain open during the entire interval in which the shuntcircuit is. completed through the dash pot. This is'accomplished bymaking return spring |59 stronger than the spring supporting contact itiof switch |50. The actual shunting of the ignition circuit is thereforelimited to the return movement of piston |60 which provides suiiicienttime to allow the pressure to drop behind pistons 3I. vThe time elapsingbetweenthe actuation of valve 82 and the shunting of the ignition-circuit may be approximately half a second. The duration of the shuntcan be predetermined by a proper relation between the 'strength ofreturn spring |59 and the uid leak in the dash pot so as not to exceed,for example. one-quarter of a second.

Pistons 3l are subject to centrifugal forcewhich varies as the square ofthe speed of the vehicle. The size of the pistons and the magnitude ofthe retractive effort of springs 31 and the unbalanced hydraulicpressure may be so predetermined as to prevent the retraction of thepistons at speeds at which torque multiplication through the converteri2 isl no longer possible, since at such speeds no-advantage can begained by driving through the converter instead of through the clutchi1.

It is understood that the fasteners, bearings, and gaskets necessary forthe operation of a device of the class described may be arranged to suitthe designer and accordingly are not described herein in detail. It isunderstood further that the foregoing description is merely illustrativeof a preferred embodiment and that the scope of the invention thereforis not to be limited thereto but is to be determined by the appendedclaims.

y We claim:

l. A transmission comprising a drive shaft, a driven shaft, torqueconverting mechanism, reversing mechanism of the differential typehaving at least three cooperating elements, one of said elements beingconnected to the driven shaft, means connecting the torque convertingmechanism with the driving shaft, means continuously effective toconnect the torque converting mechanism with another of said elements,releasable means connecting the torq'ue yconverting mechanism with thedriven shaft to provide parallel connections between the torqueconverting mechanism and the driven shaft,`means for arresting therotation of a third element to change the direction of rotation of thedriven shaft with re-v spect to the drive shaft, and means associatedwith the arresting means for releasing the re-' leasable connectionbefore the rotation ofthe third element is arrested` 2. A transmissioncomprising driving and driven shafts, hydraulically controlled devicesfor connecting the shafts in different speed ratios..a.

'ascuas 'hydraulic system deriving its power from the drive shaft forcontrolling some of said devicesv only, a. second hydraulic systemderiving its power from the driven shaft for controlling at least onedevice not controlled by the rst system. said second system having anormally uncovered bleed opening which prevents a building up ofoperat-Y ing pressure in said system except above a predetermined speedof the driven shaft, thereby preventing a speed ratio change through thedevice controlled by said system until said predetermined speed isattained, andmeans for insuring a full ratio change at saidpredetermined speed, thereby preventinga long slip period inV theconnecting device.

3. A transmission comprising a drive shaft, a driven shaft, torqueconverting mechanism and a reversing mechanism connected in seriesbetween the shafts, said reversing mechanism com prising a plurality ofrelatively rotatable elements one of which is non-releasably connectedto the driven shaft, positive means for arresting the rotation ofasecond element and means for relating the movement of the third elementto the movement of the driven shaft whereby to facilitate the arrest ofthe second element when the drivenshaft is not rotated.

4. A transmission for a vehicle comprising a drive shaft, a driven shaftassociated with the wheels of the vehicle and-movable in timed relationtherewith, torque converting mechanism connected between said shafts andincluding differential gearing having one element connected to thedriven shaft, positive means operable when the transmission isconditioned for reverse for arresting the rotation of a second element,and friction means effective when the vehicle is not in motion forarresting the rotation of the sec ond element through the intermediaryof a third element for assisting the operation of the positive arrestingmeans.

5, A transmission comprising a drive shaft, a driven shaft.' torqueconverting mechanism connected between said shafts and includingplanetary gearing having a ring gear connected to the driven shaft, acarrier and a sun gear, positive means operable'when the transmission isconditioned for reverse for engaging the carrier to arrest the rotationthereof and friction means cooperating through the intermediary of thesun gear'and the driven shaft to assist in arresting the rotation ofthecarrier to facilitate the engagement of the positive means.

6. A transmission for a vehicle as described in claim 4, and controlmeans for the positive meansl and for the friction means, said controleffecting a sequential movement of the positive and friction means suchthat during the first portion of the movement of the control means thefriction means becomes effective and is then released just prior to theengagement of the positive means.

7. A transmission for a vehicle comprising a. drive shaft, a drivenshaft. and torque converting mechanism connected between said shafts,said mechanism including a rotatable element the rotation of which maybe arrested to effect a speed change through the mechanism, positive'means for arresting the rotation of the element, a second element, fluidcontrolled means for associating the second 'element with the drive'nshaft and with the first-mentioned element to relate the movement orlack of movement of the driven shaft to-the movement of the first-men#-tioned element, and a valve controlling the-fluid means, said valvebeing mechanically connected to the positive arresting means;

8. A transmission as described in claim 7, said valve having portingswhich permit the fluid controlled means to operate upon the initialmovement of the positive means in its arresting movement and whichrelease the fluid controlled means just prior to the engagement of thepositive means.

9. A transmission comprising a drive shaft, a

riven shaft, torque converting mechanism connected to the drive shaft, aring gear connected to the driven shaft, a sun gear non-releasablyconnected to the said mechanism, planet pinions meshing with the sun andring gears, a carrier for the planets, a toothed element connected tothe carrier, a cooperating toothed device for engaging the toothedelement to hold the said element against rotation, a clutch forconnecting the torque converting mechanism to thev driven shaft, fluidmeans for operating the clutch, a

valve for controlling the fluid means, a manual control element, andmeans connecting the control element to the toothed device and to thevalve to cause the valve to move in timedrelation to the toothed device,said valve having portings which cause the clutch to engage prior to theengagement of the toothed device with the toothed element to lock thecarrier and its associated toothed element to the driven shaft and thenrelease the clutch immediately before the toothed device engages thetoothed element.

10. In a torque transmitting mechanism for a. prime mover having a speedregulator, uid control means for transmitting the torque of the primemover, a valve for controlling the fluid means, and means connecting thevalve to the speed regulator, said means including an overcenter devicefor preventing a movement of the valve except at the extreme positionsof the speed regulator, and said overcenter device comprising a pivotedarm` connected at its free end to the speed regulator, an arm connectedto the valve, and a compressible medium connecting the arms, said armsbeing adapted to swing past oneA another to alternatelyV compress andrelease said medium.

11. In a torque transmitting mechanism for a prime mover having anignition system, means for multiplying the torque of the prime mover,positive clutch means in parallel with the torque multiplying means,said positive clutch means having a movable element for controlling theengagement and disengagement thereof, means for impressing a force uponthe movable member of the clutch while the clutch is in engagedcondition, said force being applied in a, direction to release theclutch such that pending the release of torque on the clutch itself thereleasing force is ready to move the clutch to released position, andmeans for relieving the -torque on the clutch when the releasing forceis established, said torque-relieving means comprising a normally brokencircuit in parallel with the' ignition circuit, means for establishingthe circuit, and mechanical means controlling the circuit establishingmeans.

12. In a torque transmitting mechanism for a. prime mover having anignition circuit, a positive coupling device, means for establishing areleasing bias'on the device, means for relieving .the torque on thedevice comprising a normally broken circuit in parallel with theignition circuit, means for establishing the normally broken circuit,dash pot means for controlling the operation of the circuit establishingmeans, and means for coordinating operation of the bias establishingmeans with the operation of the dash pot.

v HAROLD NUIT.

RICHARD L. SMIRL.

